Ranging method, ranging device, location device and location method

ABSTRACT

A ranging method, executed in a ranging device, comprising steps of: obtaining a trip time of a received wireless signal, wherein the received wireless signal is a wireless signal from an object; calculating a statistical value of a rising time of the received wireless signal; correcting the trip time according to the statistical value of the rising time; and estimating a distance between the object and the ranging device according to the corrected trip time.

BACKGROUND

1. Technical Field

The present disclosure relates to a ranging method, in particular, to aranging method and device considering the statistical value (forexample, the standard deviation, i.e. time spread, while considering thenoise is the additive white Gaussian noise (AWGN)) of the rising time ofthe received wireless ranging signal due to the noise, and to a locationmethod and device using the ranging method or device.

2. Description of Related Art

The ranging method or device is used to estimate a distance between anobject and a ranging device by using a wireless ranging signal. Onecurrently marketed ranging device can detect the signal strength decayof the received wireless ranging signal to estimate the distance betweenthe object and the ranging device, since the wireless ranging signal isattenuated along with the distance ideally. However, the signal strengthdecay is actually further in response to the channel response, such thatthis ranging device must obtain the channel response. Since a channelestimator may be required to obtain the channel response, the rangingdevice for detecting the signal strength decay of the received wirelessranging signal has large cost. Furthermore, if the channel is fastchanged (i.e. not a static channel), the estimated distance between theobject and the ranging device may have large difference to the actualdistance between the object and the ranging device.

Furthermore, strength of received signal can be reasonable reduced bywhich the objects absorb the electromagnetic wave (EMW) propagated fromthe transmitter to the receiver. If such object (or objects) areobstructing first Fresnel zone, then level of received signal (radiosignal strength, RSSI) is reasonably reduced. Objects which can heavilyabsorb EMW are thick concrete walls (especially when concrete wall iswet), layers of coal (in coal mines), water, and the similar ones.

As consequence, the distance estimation based on free space propagationmodel is loaded by big error, wherein the value of the error increaseswith additional attenuation, reflection, diffusion diffraction andsimilar physical effects caused by surrounding objects (these effectsare depending on their nature, dimensions, electrical properties, and soon).

Another currently marketed ranging device can calculate or count thetrip time of the received wireless ranging signal to estimate thedistance between the object and the ranging device, wherein the triptime comprises the rising time of the received wireless ranging signalsince the trip time is the time difference between the rising time ofthe received wireless ranging signal and the rising time of the emittedwireless ranging signal, i.e. the trip time is also called delay time.However, since the channel inevitably has the noise, the rising time ofthe received wireless ranging signal is spread, i.e. the rising time ofthe received wireless ranging signal is lengthened. Thus, the estimateddistance between the object and the ranging device may be shorter thanthe actual distance between the object and the ranging device.

Moreover, the location device may use the ranging device, wherein theranging device is used to estimate the distances between the objects andthe ranging device, and the location device can determined the locationof the location device according to the estimated distances. Oralternatively, the distances between the object and the ranging devicesare estimated by the ranging devices, and the location device candetermine the location of the object according to the estimateddistances. However, the higher the ranging accuracy of the rangingdevice is, the higher the location accuracy of the location device is.Thus, a ranging device with a precise accuracy is needed.

SUMMARY

An exemplary embodiment of the present disclosure provides a rangingmethod executed in a ranging device. The ranging method comprises stepsof: obtaining a trip time of a received wireless signal, wherein thereceived wireless signal is a wireless signal from an object;calculating a statistical value of a rising time of the receivedwireless signal; correcting the trip time according to the statisticalvalue of the rising time; and estimating a distance between the objectand the ranging device according to the corrected trip time.

Another exemplary embodiment of the present disclosure further providesa ranging device comprising a physic module, a medium access controlmodule, a controller, and a ranging module, wherein the medium accesscontrol module is connected to the physic module, the a controller isconnected to the medium access control module, and a ranging module,connected between the medium access control module, and the controlleris connected between the medium access control module and thecontroller. The physic module receives a wireless signal. The rangingmodule executes the steps of the above ranging method.

Furthermore, an exemplary embodiment of the present disclosure furtherprovides location method and device using the above ranging device ormethod, wherein the ranging device or method may estimate severaldistances between several objects and the location device, and thelocation of the location device is thus determined by the estimateddistances.

Moreover, in one exemplary embodiment of the present disclosure, whileconsidering a noise is an additive white Gaussian noise, the statisticalvalue of the rising time is a standard deviation of the rising time.

To sum up, the ranging and location methods or devices provided in thepresent disclosure has the larger accuracies than those of theconventional ranging and location methods or devices.

In order to further understand the techniques, means and effects of thepresent disclosure, the following detailed descriptions and appendeddrawings are hereby referred, such that, through which, the purposes,features and aspects of the present disclosure can be thoroughly andconcretely appreciated; however, the appended drawings are merelyprovided for reference and illustration, without any intention to beused for limiting the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated in andconstitute a part of this specification. The drawings illustrateexemplary embodiments of the present disclosure and, together with thedescription, serve to explain the principles of the present disclosure.

FIG. 1A is a schematic diagram showing a ranging theory according to oneexemplary embodiment of the present disclosure.

FIG. 1B is a wave diagram showing a wireless ranging signal emitted froma ranging device and an ideal wireless acknowledge signal responded(sent back) from an object according to one exemplary embodiment of thepresent disclosure.

FIG. 2A is a schematic diagram showing a ranging theory according toanother exemplary embodiment of the present disclosure.

FIG. 2B is a wave diagram showing an ideal received wireless rangingsignal according to one exemplary embodiment of the present disclosure.

FIG. 3 is a wave diagram showing the received wireless signal in realworld according to one exemplary embodiment of the present disclosure.

FIG. 4 is a block diagram showing the ranging device according to oneexemplary embodiment of the present disclosure.

FIG. 5 is a schematic diagram showing a location theory according to oneexemplary embodiment of the present disclosure.

FIG. 6 is a block diagram of a location device according one exemplaryembodiment of the present disclosure.

FIG. 7A is a flow chart of a ranging method according to one exemplaryembodiment of the present disclosure.

FIG. 7B is a flow chart of a ranging method according to anotherexemplary embodiment of the present disclosure.

FIG. 7C is a flow chart of a ranging method according to anotherexemplary embodiment of the present disclosure.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or similarparts.

The details of the ranging method, the ranging device, the locationmethod, and the location device are described as follows, but it isnoted that the following exemplary embodiments are not used to limit thepresent disclosure.

[Exemplary Embodiment of Ranging Device]

Referring to FIG. 1A, FIG. 1A is a schematic diagram showing a rangingtheory according to one exemplary embodiment of the present disclosure.The ranging device is provided and equipped in the base station 10, andthe ranging device comprises circuits for estimating a distance betweenan object 12 (such as the car) and the ranging device (or base station10).

In the exemplary embodiment, the ranging device emits a wireless rangingsignal to the object 12, and the object 12 responds to the wirelessranging signal emitted from the ranging device by sending back awireless acknowledge signal; or alternatively the object 12 reflects thewireless ranging signal, and thus a wireless reflection signal from theobject 12 propagates to the ranging device. Herein, to illustratebriefly and concisely, in the following descriptions, the wirelessacknowledge signal is used as an example to state the principle of theranging method of the exemplary embodiment in the present disclosure,but the present disclosure however is not limited thereto. It is obviousthat the wireless acknowledge signal in the following descriptionrelative to the exemplary embodiment of FIG. 1A and FIG. 1B can bereplaced by the wireless reflection signal.

The ranging device receives the wireless acknowledge signal from theobject 12 (relied by the object 12). It is obvious that the wirelessranging signal and the wireless acknowledge signal travel a distance of2R, and the distance between the object 12 and the ranging device (i.e.base station 10) is R.

Referring to FIG. 1A and FIG. 1B, FIG. 1B is a wave diagram showing awireless ranging signal emitted from a ranging device and an idealwireless acknowledge signal responded (or sent back) from an objectaccording to one exemplary embodiment of the present disclosure. Theideal wireless acknowledge signal responded (or sent back) from theobject 12 is received by the ranging device, and the trip time (orcalled delay time) of the ideal received wireless acknowledge signal ist_(R) (after deduction of internal processing times). To put itconcretely, the trip time t_(R) of the ideal received wirelessacknowledge signal is the time difference between the rising timet_(rise2) of the ideal received wireless acknowledge signal (the signalin the bottom side of FIG. 1B) and the rising time t_(rise1) of theemitted wireless ranging signal (the signal in the upper side of FIG.1B). Counting the trip time t_(R) (start and stop events) happens whenthe signal level crosses certain level determined by the threshold. Thelevel of the threshold is selected between minimum (0%) and maximum(100%) of the ideal amplitude—usually about 50% ideal amplitude. Theranging device can estimate the trip time t_(R) of the ideal receivedwireless acknowledge signal, and based on the estimated trip time t_(R)of the ideal received wireless acknowledge signal, the distance betweenthe object 12 and the ranging device 10 is thus estimated, i.e.R=ct_(R)/2.

Referring to FIG. 2A, FIG. 2A is a schematic diagram showing a rangingtheory according to another exemplary embodiment of the presentdisclosure. In the exemplary embodiment, the ranging device is providedand equipped in the cell phone 14, and the ranging device comprisescircuits for estimating a distance R between an object 13 (such as basestation) and the ranging device.

In the exemplary embodiment, the object 13 emits a wireless rangingsignal to the ranging device, and the ranging device receives thewireless ranging signal. It is obvious that the wireless ranging signaltravels a distance of R, and the distance between the object 13 and theranging device (i.e. cell phone 14) is R.

Referring to FIG. 2A and FIG. 2B, FIG. 2B is a wave diagram showing anideal received wireless ranging signal according to one exemplaryembodiment of the present disclosure. The wireless ranging signal isreceived by the ranging device, and the ranging device can obtain therising time t_(Emitted) of the emitted wireless ranging signal. The triptime (or called delay time) of the ideal received wireless rangingsignal is t_(R). To put it concretely, the trip time t_(R) of the idealreceived wireless ranging signal is the time difference between therising time t_(rise) of the ideal received wireless ranging signal andthe rising time t_(Emitted) of the emitted wireless ranging signal. Theranging device can estimate the trip time t_(R) of the ideal receivedwireless ranging signal, and based on the estimated trip time t_(R) ofthe received wireless ranging signal, the distance between the object 13and the ranging device is thus estimated, i.e. R=ct_(R).

It is noted that the above scenario of the application of the rangingdevice is not used to limit the present disclosure. The ranging deviceor method provided by the present disclosure can be applied to all typesof time based measurement (estimation) techniques, like round trip offlight (RToF) of one way, two ways, or symmetrical-double sided, timedifference of arrival (TDoA), and so on. The ranging device or methodprovided by the present disclosure can be further applied to angle basedtechniques, such as angle of arrival (AoA), angle of departure (AoD) andso on.

Referring to FIG. 3, FIG. 3 is a wave diagram showing the receivedwireless signal in real world according to one exemplary embodiment ofthe present disclosure. The channel inevitably has noise n(t), thus therising edge of the received wireless signal (such as the receivedwireless ranging, acknowledge, or reflection signal) crosses thresholdlevel earlier by time Δt_(rise) such that the accuracy of the estimateddistance is affected. Given a specific threshold, such as 50% idealamplitude A of the received wireless signal, the rising time t_(rise) ofthe received wireless ranging signal is the time that the amplitude ofthe received wireless signal exceeds 0.5 A.

It is noted that the specific threshold can be determined according tothe different requirement. In one exemplary embodiment, the specificthreshold be can related to the average maximum amplitude avg(A+n(t)) ofthe received wireless signal and the average minimum amplitude avg(n(t))of the received wireless signal, and the equation of the specificthreshold can be expressed as, threshold=(avg(A+n(t))k₁+avg(n(t))k₂),wherein the variables k₁ and k₂ are respectively the weighting factors,for example the weighting factors k₁ and k₂ are 0.4, but the presentdisclosure is not limited.

Furthermore, the specific threshold can be an optimum threshold, and theoptimum threshold can be determined by the differentiation of thereceived wireless signal in time domain. The differentiation of thereceived wireless signal has the maximum at a specific time, and theamplitude of the received wireless signal at the specific time can beset as the optimum threshold.

Due to the noise n(t), the rising edge of received wireless signalcrosses threshold level earlier by time t_(rise), so the measured errorequals to Δt_(rise) (i.e. standard deviation in the statistics whileconsidering the noise n(t) is the AWGN) of the rising time t_(rise). Asshown in FIG. 3, the rising time t_(rise) of the ideal received wirelesssignal and the rising time t_(rise) of the actual received wirelesssignal with the noise n(t) have the measured error Δt_(rise) of therising time t_(rise).

A slope of the received wireless signal can be obtained by the followingexpression, slope=A/t_(rise). The slope of the received wireless signalis then expressed related to noise and the measured error Δt_(rise) ofthe rising time t_(rise), and the expression is slope=n(t)/Δt_(rise).Then, the measured error Δt_(rise) of the rising time t_(rise) can beexpressed as follows,

${{\Delta\; t_{rise}} = {{{slope}/{n(t)}} = {\frac{n(t)}{\left( \frac{A}{t_{rise}} \right)} = \frac{t_{rise}}{\sqrt{\frac{A^{2}}{{n(t)}^{2}}}}}}},$wherein A²/n(t)² is the baseband signal-to-noise power ratio of thereceived wireless signal.

Considering a linear detector law and a large signal-to-noise ratio, thebaseband signal-to-noise power ratio is twice the intermediate frequency(IF) signal-to-noise power ratio S/N, and the measured error Δt_(rise)of the rising time t_(rise) can be expressed as follows,

${\Delta\; t_{rise}} = {\frac{t_{rise}}{\sqrt{\frac{2\; S}{N}}}.}$

Then, if the rising time t_(rise) of the received wireless signal islimited by the bandwidth B of the IF amplifier, the rising time t_(rise)is about 1/B. Letting S=E_(S)/t_(d) and N=N₀B, the measured errorΔt_(rise) of the rising time t_(rise) can be expressed as follows,

${{\Delta\; t_{rise}} = {\frac{t_{rise}}{\sqrt{\frac{2\; S}{N}}} = \sqrt{\frac{t_{d}N_{0}}{2\;{BE}_{S}}}}},$wherein E_(S) is signal energy of the received wireless signal, t_(d) isthe duration of the received wireless signal, and N₀ is the powerspectral density (PSD) of the noise n(t).

If the same independent time delay measurement is done on the fallingedged of the received wireless signal, then the measurement results fromtwo combined and averaged individual measurements is improved by asquare root of 2, and the measured error Δt_(rise) of the rising timet_(rise) can be expressed as follows,

${\Delta\; t_{rise}} = {{\frac{1}{\sqrt{2}}\frac{t_{rise}}{\sqrt{\frac{2\; S}{N}}}} = {\frac{1}{2}{\sqrt{\frac{t_{d}N_{0}}{{BE}_{S}}}.}}}$

It is noted that the measured error Δt_(rise) of the rising timet_(rise) is the root mean square (i.e. standard deviation) of thedifference between the measured value and the true value. Thedisturbance limiting the accuracy of the distance measurement is assumedto be the receiver noise. It is furthermore assumed that bias errorshave been removed. Radar theory states the relationship between standarddeviation of the rising time t_(rise), an effective bandwidth B_(eff),and the signal-to-noise ratio E_(S)/N₀ as follows:

${\Delta\; t_{rise}} = {{{std\_ dev}\left( t_{rise} \right)} = {\frac{1}{B_{eff}\sqrt{2\left( \frac{E_{S}}{N_{0}} \right)}}.}}$Furthermore, the effective bandwidth B_(eff) is expressed as:

${B_{eff}^{2} = {\frac{1}{E_{S}}{\int_{- \infty}^{\infty}{\left( {2\pi\; f} \right)^{2}\left( {{S(f)}} \right)^{2}\ {\mathbb{d}f}}}}},$wherein the variable f is the frequency, and the function S(f) is thespectrum of received wireless signal. It is noted that the effectivebandwidth B_(eff) is the same as the root mean square bandwidth B_(rms).

If the received wireless signal has a frequency band limited signal(with a frequency bandwidth Δf) spectrum at the base band, like thechirp with the constant spectrum magnitude (i.e. |S(f)|=1 in-band, and|S(f)|=0 otherwise), the effective bandwidth B_(eff) can be expressedas,

$B_{eff}^{2} = {{\frac{1}{E_{S}}{\int_{{- 0.5}\Delta\; f}^{0.5\Delta\; f}{\left( {2\pi\; f} \right)^{2}\left( {{S(f)}} \right)^{2}\ {\mathbb{d}f}}}} = {{\frac{4\pi^{2}}{E_{S}}{\int_{{- 0.5}\Delta\; f}^{0.5\Delta\; f}{f^{2}{\mathbb{d}f}}}} = {\frac{\pi^{2}}{3\; E_{S}}\Delta\;{f^{3}.}}}}$That is, the effective bandwidth B_(eff) can be expressed as,

$B_{eff} = {\sqrt{\frac{\pi^{2}}{3\; E_{S}}\Delta\; f^{3}}.}$

Furthermore, if the received wireless signal has the continuous sharprectangular waveform with period t_(d), the root mean square bandwidthB_(rms) (i.e. B_(eff)) can be expressed as follows,

$B_{rms}^{2} = {\frac{\int_{- \infty}^{\infty}{\left( {2\pi\; f} \right)^{2}\left( {{S(f)}} \right)^{2}\ {\mathbb{d}f}}}{\int_{- \infty}^{\infty}{\left( {{S(f)}} \right)^{2}\ {\mathbb{d}f}}} = {\frac{\int_{- \infty}^{\infty}{\left( {2\pi\; f} \right)^{2}\frac{{\sin\left( {\pi\;{ft}_{d}} \right)}^{2}}{\left( {\pi\; f} \right)^{2}}\ {\mathbb{d}f}}}{\int_{- \infty}^{\infty}{\frac{{\sin\left( {\pi\;{ft}_{d}} \right)}^{2}}{\left( {\pi\; f} \right)^{2}}\ {\mathbb{d}f}}} = {{\frac{1}{E_{S}}{\int_{- \infty}^{\infty}{\left( {2\pi\; f} \right)^{2}\left( {{S(f)}} \right)^{2}\ {\mathbb{d}f}}}} = {\frac{4}{E_{S}}{\int_{- \infty}^{\infty}{{\sin\left( {\pi\;{ft}_{d}} \right)}^{2}\ {{\mathbb{d}f}.}}}}}}}$Since the spectrum bandwidth is limited to B, the above equation of theroot mean square bandwidth can expressed as follows,

$B_{rms}^{2} = {\frac{4}{E_{S}}{\int_{{- 0.5}\; B}^{0.5\; B}{{\sin\left( {\pi\;{ft}_{d}} \right)}^{2}\ {{\mathbb{d}f}.}}}}$After several calculation have been done, the root mean square bandwidthB_(rms) (i.e. B_(eff)) can be expressed as follows,

$B_{rms} = {\sqrt{\frac{1}{t_{d}^{2}}\frac{{\pi\;{Bt}_{d}} - {\sin\left( {\pi\;{Bt}_{d}} \right)}}{{{Sin}\;{c\left( {\pi\;{Bt}_{d}} \right)}} + \frac{{\cos\left( {\pi\;{Bt}_{d}} \right)} - 1}{\pi\;{Bt}_{d}}}}.}$

It is noted that the standard deviation is optimal for the AWGNstatistic. For other types of noises and interferences (especiallyHuman-made interferences, having regular time-frequency pattern),another statistical measure can be optimal—not always standarddeviation. The following exemplary embodiments are illustrated whiletaking the statistical value of the rising time is the standarddeviation of the rising time, but the present disclosure is however notlimited thereto.

Referring to FIG. 4 is a block diagram showing the ranging deviceaccording to one exemplary embodiment of the present disclosure. Theranging device comprises a ranging module 40, a controller 41, a mediumaccess control (MAC) module 42, and a physical layer (PHY) module 43.The MAC module 42 is connected to the controller 41 and the PHY module43, and the ranging module 40 is connected between the MAC module 42 andthe controller 41.

The PHY module 43 can receive the wireless signal from somewhere, suchas the wireless ranging, acknowledge, or reflection signal. The PHYmodule 43 can further emit the wireless signal, such as the wirelessranging, acknowledge, or reflection signal. Based upon at least one ofthe above equations, the ranging module 40 considers the standarddeviation Δt_(rise) of the rising time t_(rise) of the received wirelesssignal to estimate the distance between the ranging device and theobject. The ranging module 40 can further indicates the controller 41 toadjust at least one parameter related to the standard deviationΔt_(rise) of the rising time t_(rise).

In one exemplary embodiment of the present disclosure, the rangingmodule 40 calculates the standard deviation Δt_(rise) of the rising timet_(rise), corrects the trip time t_(R) of the received wireless signalaccording to the standard deviation Δt_(rise) of the rising timet_(rise), and then estimate the distance between the ranging device andthe object according to the corrected trip time of the received wirelesssignal.

The standard deviation Δt_(rise) of the rising time t_(rise) can becalculated according to the effective bandwidth B_(eff), the signalenergy E_(S), and the power spectral density of noise N₀. Oralternatively, the standard deviation Δt_(rise) of the rising timet_(rise) can be calculated according to the signal energy E_(S), thepower spectral density of noise N₀, the bandwidth of the IF amplifier,and the duration of the received wireless signal. It is noted that thecalculation manner of the standard deviation Δt_(rise) of the risingtime t_(rise) is not used to limit the present disclosure.

In another exemplary embodiment of the present disclosure, the rangingmodule 40 calculates the standard deviation Δt_(rise) of the rising timet_(rise), and determines whether the standard deviation Δt_(rise) of therising time t_(rise) is smaller than a specific value. If the standarddeviation Δt_(rise) the rising time of t_(rise) is smaller than aspecific value, the ranging module 40 determines that the standarddeviation Δt_(rise) of the rising time t_(rise) lightly affects triptime t_(R) of the received wireless signal, and the ranging module 40estimates the distance between the ranging device and the objectaccording to the trip time t_(R) of the received wireless signal. If thestandard deviation Δt_(rise) of the rising time t_(rise) is not smallerthan a specific value, the ranging module 40 determines that thestandard deviation Δt_(rise) the rising time t_(rise) seriously affectstrip time t_(R) of the of received wireless signal, thus the rangingmodule 40 indicates the controller 41 to adjust one of parametersrelated to the standard deviation Δt_(rise) the rising time of t_(rise),and then performs a ranging action again to obtain the standarddeviation Δt_(rise) of the rising time t_(rise) in response to the leastone adjusted parameter. Therefore, the ranging device can eliminate thestandard deviation Δt_(rise) of the rising time t_(rise) to increase theranging accuracy.

Based upon the above descriptions, the effective bandwidth B_(eff), thesignal energy E_(S), the bit energy E_(b), the bit energy to noise ratioE_(b)/N₀, the pulse shape or type of the wireless signal used, and thespecific threshold can be adjusted to decrease the standard deviationΔt_(rise) of the rising time t_(rise). For example, the correlativesignal can be used as the emitted or responded wireless signal, whereinthe correlative signal use both “complementary” representations, such asthe correlative signal has the up-chirp and the down-chirp. It is notedthat the both “complementary” representations of the correlative signalmay have different weighting, for example, the up-chirp and thedown-chirp have the different absolute amplitudes.

In another exemplary embodiment of the present disclosure, the rangingmodule 40 selects one parameter set which minimizes the standarddeviation Δt_(rise) of the rising time t_(rise) the received wirelesssignal among a of plurality of parameter sets under a specificconstraint. Each parameter set comprises at least one parameter relatedto the standard deviation Δt_(rise) of the rising time t_(rise) of thereceived wireless signal.

Based upon the above descriptions, the effective bandwidth B_(eff), thesignal energy E_(S), the bit energy E_(b), the bit energy to noise ratioE_(b)/N₀, the pulse shape or type of the wireless signal used, and thespecific threshold can be adjusted to decrease the standard deviationΔt_(rise) the rising time of t_(rise). Under a specific constraint, forexample, a constraint of cost and signal energy E_(S) constraint, one ofthe pulse shapes or types of the wireless signals which minimizes thestandard deviation Δt_(rise) of the rising time t_(rise) is selected bythe ranging device, so as to increase the ranging accuracy.

[Exemplary Embodiment of Location Device]

Referring to FIG. 5, FIG. 5 is a schematic diagram showing a locationtheory according to one exemplary embodiment of the present disclosure.In the exemplary embodiment, the cell phone 24 may be equipped thelocation device, and the location device obtains the distances R1through R3 between the cell phone 24 and the base stations 20 through22. Based upon the distances R1 through R3, the location device candetermine the location of the cell phone 24.

Referring to FIG. 6, FIG. 6 is a block diagram of a location deviceaccording one exemplary embodiment of the present disclosure. Theranging device comprises a location module 60, a controller 61, a mediumaccess control (MAC) module 62, and a physical layer (PHY) module 63.The MAC module 62 is connected to the controller 61 and the PHY module63, and the location module 60 is connected between the MAC module 62and the controller 61.

The PHY module 63 can receive the wireless signal from somewhere, suchas the wireless ranging, acknowledge, or reflection signal. The PHYmodule 63 can further emit the wireless signal, such as the wirelessranging, acknowledge, or reflection signal. Based upon at least one ofthe above equations, the location module 60 obtains the information ofthe distances between the objects and the location device. The distancescan be obtained from the above description considering the standarddeviation Δt_(rise) of the rising time t_(rise) of the received wirelesssignal. The location module 60 can further indicates the controller 61to adjust at least one parameter related to the standard deviationΔt_(rise) of the rising time t_(rise).

[Exemplary Embodiment of Ranging Method]

FIG. 7A is a flow chart of a ranging method according to an exemplaryembodiment of the present disclosure. At step S701, a trip time of thereceived wireless signal (such as the wireless ranging signal emittedfrom the object, the wireless acknowledge signal responded from theobject, or the wireless reflection signal from the object) is receivedby the ranging device. At step S702, the ranging device calculates astandard deviation of a rising time of the received wireless signal,wherein the calculation manner of the standard deviation of a risingtime of the received wireless signal is illustrated in the abovedescriptions, thus omitting the details to calculate the standarddeviation of the rising time. At step S703, the ranging device uses thestandard deviation of the rising time to correct the trip time of thereceived wireless signal. At step S704, the ranging device estimates adistance between the object and the ranging device according to thecorrected trip time.

FIG. 7B is a flow chart of a ranging method according to an exemplaryembodiment of the present disclosure. At step S711, a trip time of thereceived wireless signal is received by the ranging device, wherein thereceived wireless signal is the wireless signal from the object (such asthe wireless ranging signal emitted from the object, the wirelessacknowledge signal responded from the object, or the wireless reflectionsignal from the object). At step S712, the ranging device calculates astandard deviation of a rising time of the received wireless signal,wherein the calculation manner of the standard deviation of a risingtime of the received wireless signal is illustrated in the abovedescriptions, thus omitting the details to calculate the standarddeviation of the rising time. At step S713, the ranging device evaluateswhether the standard deviation of the rising time is smaller than aspecific value.

If the standard deviation of the rising time is smaller than a specificvalue, step S714 is executed; otherwise, step S715 is executed. At stepS714, the ranging device estimates a distance between the object and theranging device according to the corrected trip time, wherein thecorrected trip time is generated by using the standard deviation of therising time to correct the trip time. At step S715, the ranging deviceadjusts at least one of parameter related to the standard deviation ofthe rising time. After the at least one parameter related to thestandard deviation of the rising time is adjusted, a ranging action isexecuted again, i.e. the trip time of the received wireless signal inresponse to the least one adjusted parameter is received by the rangingdevice at the re-executed step S711. It is noted that, in FIG. 7B, theexecution number which the step S711 is executed may be calculated. Ifthe execution number is larger than a specific value, the ranging methodis thus terminated, and such a measuring error report is reported.

FIG. 7C is a flow chart of a ranging method according to anotherexemplary embodiment of the present disclosure. At step S721, among aplurality of parameter sets under a specific constraint, the rangingdevice selects one parameter set which minimizes the standard deviationof the rising time of the received wireless signal, wherein eachparameter set comprises at least one parameter related to the standarddeviation of the rising time of the received wireless signal. Then, atstep S722, a trip time of the received wireless signal is received bythe ranging device, and at step S723, the ranging device estimates adistance between the object and the ranging device according to thecorrected trip time, wherein the corrected trip time is generated byusing the standard deviation of the rising time to correct the triptime.

[Exemplary Embodiment of Location Method]

A location method using one of the above ranging methods is provided inthe present disclosure. Firstly, the distances between the objects andthe location device are estimated by using the ranging method of thepresent disclosure, and then the location device determines the locationof the location device according to the distances between the objectsand the location device.

[Results of Exemplary Embodiment]

To sum up, the ranging and location methods or devices provided in thepresent disclosure has the larger accuracies than those of theconventional ranging and location methods or devices.

The above-mentioned descriptions represent merely the exemplaryembodiment of the present disclosure, without any intention to limit thescope of the present disclosure thereto. Various equivalent changes,alternations or modifications based on the claims of present disclosureare all consequently viewed as being embraced by the scope of thepresent disclosure.

What is claimed is:
 1. A ranging device, comprising: an antenna module,for receiving a wireless signal; a medium access control module,connected to the antenna module; a controller, connected to the mediumaccess control module; and a ranging module, connected between themedium access control module and the controller, for executing followingsteps: obtaining a trip time of a received wireless signal, wherein thereceived wireless signal is a wireless signal from an object;calculating a statistical value of a rising time of the receivedwireless signal; determining whether the statistical value of the risingtime of the received wireless signal is smaller than a specific value;when the statistical value of the rising time of the received wirelesssignal is smaller than the specific value, estimating a distance betweenthe object and the ranging device according to the trip time of thereceived wireless signal; and when the statistical value of the risingtime of the received wireless signal is not smaller than the specificvalue, estimating the distance between the object and the ranging deviceaccording to a corrected trip time, wherein the statistical value of therising time of the received wireless signal corrects the trip time ofthe received wireless signal to generate the corrected trip time.
 2. Theranging device according to claim 1, wherein while considering a noiseis an additive white Gaussian noise, the statistical value of the risingtime is a standard deviation of the rising time.
 3. A location device,comprising: an antenna module, for receiving a wireless signal; a mediumaccess control module, connected to the antenna module; a controller,connected to the medium access control module; and a location module,connected between the medium access control module and the controller,for executing following steps: obtaining distances between the locationdevice and objects; and determining a location of the location deviceaccording to the distances; wherein each distance between the locationdevice and the object is obtained by following steps: obtaining a triptime of a received wireless signal, wherein the received wireless signalis a wireless signal from an object; calculating a statistical value ofa rising time of the received wireless signal; determining whether thestatistical value of the rising time of the received wireless signal issmaller than a specific value; when the statistical value of the risingtime of the received wireless signal is smaller than the specific value,estimating a distance between the object and the location deviceaccording to the trip time of the received wireless signal; and when thestatistical value of the rising time of the received wireless signal isnot smaller than the specific value, estimating the distance between theobject and the location device according to a corrected trip time,wherein the statistical value of the rising time of the receivedwireless signal corrects the trip time of the received wireless signalto generate the corrected trip time.
 4. The location device according toclaim 3, wherein while considering a noise is an additive white Gaussiannoise, the statistical value of the rising time is a standard deviationof the rising time.
 5. The ranging device according to claim 2, whereinthe standard deviation of the rising time is calculated according to aneffective bandwidth of the received wireless signal, energy of thereceived wireless signal, and a power spectral density of noise.
 6. Theranging device according to claim 2, wherein the standard deviation ofthe rising time is calculated according to energy of the receivedwireless signal, a power spectral density of noise, a bandwidth of anintermediate frequency amplifier, and a duration of the receivedwireless signal.
 7. The ranging device according to claim 1, wherein thewireless signal is a frequency band limited signal.
 8. The rangingdevice according to claim 1, wherein the wireless signal is acomplementary signal.
 9. The location device according to claim 4,wherein the standard deviation of the rising time is calculatedaccording to an effective bandwidth of the received wireless signal,energy of the received wireless signal, and a power spectral density ofnoise.
 10. The location device according to claim 4, wherein thestandard deviation of the rising time is calculated according to energyof the received wireless signal, a power spectral density of noise, abandwidth of an intermediate frequency amplifier, and a duration of thereceived wireless signal.
 11. The location device according to claim 3,wherein the wireless signal is a frequency band limited signal.
 12. Thelocation device according to claim 3, wherein the wireless signal is acomplementary signal.